Abstract
Dendrobium catenatum polysaccharides (DCPs) have attracted attention due to their multiple physiological activities and health benefits. In this study, a novel water-soluble DCP was obtained from fresh D. catenatum stems through three-phase partitioning and ethanol precipitation at room temperature. Its structural characteristics, rheological property, and in vitro immunostimulatory activity were evaluated. Results demonstrated that DCP was a homogenous polysaccharide with a carbohydrate content of 92.75% and a weight-average molecular weight of 2.21 × 105 Da. This polysaccharide is an O-acetylated glucomannan comprised by glucose, mannose, and galacturonic acid in a molar ratio of 30.2:69.5:0.3 and mainly comprises (1→4)-β-D-mannopyranosyl (Manp), 2-O-acetyl-(1→4)-β-D-Manp, (1→6)-α-D-glucopyranosyl (Glcp), and (1→4)-α-D-Glcp residues. DCP exhibits an extended rigid chain in an aqueous solution and favorable steady shear fluid and dynamic viscoelastic behaviors. In vitro immunostimulating assays indicated that DCP activates RAW264.7 cells, thus markedly promoting macrophage proliferation and phagocytosis and increasing the levels of nitric oxide, interferon-γ, interleukin-6, and interleukin-1β. Moreover, the presence of O-acetyl group and high Mw in DCP might be responsible for its potent immunostimulatory activity in vitro. Therefore, our data suggested that DCP could be developed as a promising immunostimulant in functional food and pharmaceutical industries.
Highlights
Dendrobium catenatum Lindley (D. catenatum), generally called Tie-Pi-Shi-Hu in Chinese, is a perennial epiphytic herb belonging to Orchidaceae family [1]
After Three-phase partitioning (TPP) and ethanol precipitation, a water-soluble Dendrobium catenatum polysaccharides (DCPs) was obtained from fresh D. catenatum stems with a yield of 15.2% ± 0.6% (Figure 1)
This finding indicated that TPP combined with ethanol precipitation could effectively remove free proteins in the DCP, and this finding was similar to our earlier research [26]
Summary
Dendrobium catenatum Lindley (D. catenatum), generally called Tie-Pi-Shi-Hu in Chinese, is a perennial epiphytic herb belonging to Orchidaceae family [1]. A novel DCP was extracted and separated from fresh D. catenatum stems via TPP coupled with ethanol precipitation. The extraction and separation of DCP from fresh D. catenatum stem were carried out by TPP and ethanol precipitation method according to a previous study [19] with slight modifications. The eluant was 0.05 mol/L NaH2PO4 and 0.15 mol/L NaNO3 containing 0.02% (w/w) NaN3 (pH 7.0) at the FIGURE 1 | Extraction and isolation procedures for the DCP from fresh D. catenatum stems by using TPP and ethanol precipitation. Assay for Macrophage Phagocytosis RAW264.7 cells were seeded in a 96-well plate, incubated at 37◦C in a humidified atmosphere of 5% CO2 overnight, and treated with various concentrations (25–200 μg/mL) of DCP and LPS (4 ng/mL) for 24 h. A level of p < 0.05 signified statistical significance and indicated as follows: ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001
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